The wattmeter is an instrument for measuring the electric power in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements. Contents. 1 Electrodynamic; 2 Electronic. Dynamometer Type Wattmeter Principle: If two coils are connected such Hence an electrodynamic instrument, when connected as shown in. In electrodynamometer type wattmeter, moving coil works as pressure coil. We know that instantaneous torque in electrodynamic type instruments is directly.

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The lowest measurable current is given as 0. Unsourced material may be challenged and removed. Your email address will not be published.

The two fixed coils are air-cored to avoid hysteresis effects when used on AC. In practice accuracy can be improved by connecting a fixed load such as an incandescent light bulb, adding the device in standby, and using the difference in power consumption. It consists of following parts There are two types of coils electrodynnamic in the electrodynamometer.

Instruments with moving coils can be calibrated for direct current or power frequency currents up to a few hundred hertz. The pressure coil can also be tapped to change the meter’s range. The controlling torque is provided by springs which also serve the additional purpose of leading current into and out of the moving coil. Let I 1 and I 2 be the instantaneous values of currents in pressure and current coils respectively.

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We know that instantaneous torque in electrodynamic type instruments is directly proportional to the product of instantaneous values of currents flowing through both the coils and the rate of change of flux linked with the circuit. Electronic wattmeters are used for direct, small power measurements or for power measurements at frequencies beyond the range of electrodynamometer-type instruments.

Waveforms for switched-mode power supplies as used for much electronic equipment may be very far from sinusoidal, leading to unknown and possibly large errors at any power. Consider the arrangement shown in figure 1. Their working depends on the theory that the current carrying conductor placed in a magnetic field experiences a mechanical force.


It is, therefore, called current coil. Dynamometer type wattmeter works on very simple principle and this principle can be stated as when any current carrying conductor is placed inside a magnetic fieldit experiences a mechanical force and due to this mechanical force deflection of conductor takes place. So the expression for the torque can be written as: Earlier these fixed coils are designed to carry the electric current of about amperes but now the modern wattmeter are designed to carry electric current of about 20 amperes in order to save power.

The potential coil has, as a general rule, a high-value resistor connected in series with it to reduce the current that flows through it. In electrodynamometer type wattmetermoving coil works as pressure coil. The strength of this field is proportional to the line current and in phase with it. This is because the position of the pointer depends on the power factorvoltage and current.

The voltage across the pressure coil of the circuit is given as. There is uniform scale is used in these types of instrument as moving coil moves linearly over a range of 40 degrees to 50 degrees on either sides. The moving is air cored and is mounted on a pivoted spindle and can move freely.

Errors caused by vibration of moving system. Control System Out of two controlling systems i.

Dynamometer Type Wattmeter Working

Hence moving coil is connected across the voltage and thus the electric wagtmeter flowing through this coil is always proportional to the voltage. Scale There is uniform scale which is used in these types of instrument as moving coil moves linearly over a range of 40 degrees to 50 degrees on either side. The moving coil is connected in parallel with the load and carries the current proportional to the voltage.

A dynamometer type wattmeter essentially consists of two coils called fixed coil and moving coil.

Dynamometer Type Wattmeter Working Principle | Electrodynamometer | Electrical Academia

Now the reason is very obvious of using two fixed coils instead of one, so electrodynqmic it can be constructed to carry considerable amount of electric current.


Generally, a high resistance is connected in series with the moving coil to limit the current through it. The device consists of a pair of fixed coilsknown as current coilsand a movable coil known as the potential coil.

A typical wattmeter electfodynamic educational labs has two voltage coils pressure coils and a current coil. The readings may be displayed on the device, retained to wattmetrr a log and calculate averages, or transmitted to other equipment for further use. The moving is air cored and is mounted on a pivoted spindle and can moves freely.

So in order to limit the current we have connected the high value resistor in series with the moving coil. Errors may be due to mutual inductance effects. The pointer is fixed on the moving coil which is placed between the fixed coils. It uses for typee the power of both the AC and DC circuits.

Electrodynamometer Type Wattmeter | Electrical Study App by SARU TECH

Related pages Measurement of Three Phase Power. Advantages of Electrodynamometer Type Wattmeter Following are the advantages of electrodynamometer type wattmeter and they are written as follows: Air friction damping not shown in fig.

Air friction damping is used, as eddy current damping will distort the weak operating magnetic field and thus it may leads to error. The torque acts on the coils becomes. Because fairly large currents are required to set up the necessary field flux, the dynamometer instrument is not as sensitive as a PMMC instrument.

The content is copyrighted to ElectricalAcademia. A modern digital wattmeter samples the voltage and current thousands of times a second.

Let I 1 and I 2 be the instantaneous values of currents in pressure and electric current coils respectively. The moving coil is pivoted between the two parts of the fixed coil and is mounted on the spindle. They can be used for both to measure ac as well dc quantities as scale is calibrated for both. Did you find apk for android?